Phase Behavior And Properties Of Binary Blends And Ternary Composites Containing Carbon-based Fillers

The processibility and properties of polymers can effectively improved through blending with inorganic nano-fillers.The addition of carbon fillers can produce conductive polymer composites with high properties.The properties of conductive polymer composites are closely related to their morphologies and the distributions of conductive fillers.The phase separation of partially miscible polymer blends can be adjusted through processing conditions the types and concentrations of fillers.The mechanical,conductive properties and processability depend highly on the phase separation.Thus,conductive polymer composites with balanced properties and processability can be prepared.In this project,PMMA/SAN and SAN/PCL partially compatible blends were chosed as matrixes,CB,MWCNTs,and MWCNTs-OH were used as conductive fillers,PMMA/SAN/MWCNTs,SAN/PCL/CB,SAN/PCL/ MWCNTs,SAN/PCL/MWCNTsOH composites were prepared by melt blending.The effects of the content and type of carbon fillers,and processing temperature on the phase behaviors,rheological behaviors,mechanical properties,electrical properties,and morphologies of the composites were mainly investigated.Based on the structures,through finding the corresponding relationships between the characteristic rheological parameters and the key mechanical and electrical parameters of these composites,we try to establish a rheological method to help the compound design and molding process optimization of these composites.The results are as follows:(1)Second plateau,Cole-Cole curves,Han curves,the characteristic peaks of tan ?,and the gel-like method can be used to determine the phase separation temperatures of PMMA/SAN blends and PMMA/SAN/MWCNTs composites.The phase separation temperature of PMMA/SAN blends increased with the increase of PMMA content.The addition of MWCNTs can effectively reduce the phase separation temperature of the composites.PMMA/SAN/MWCNTs composites exhibited obvious gelation behaviors,and the physical gel point was 0.8 wt% and close to the conductive percolation value of the composites.The impact strength,tensile strength and bending strength of the composites at the gel point are all high,indicating that the mechanical,electrical properties and rheological behaviors of the composites have some corresponding relationships.(2)With the PCL content increasing,the phase separation temperature of the SAN/PCL blends decreases.The addition of 30 wt% PCL can significantly improve the impact toughness of SAN,and the blends prepared near the phase separation temperature have higher tensile and bending strength.The introduce of CB can not only effectively reduce the phase separation temperature of the SAN/PCL/CB composites,but also reduce their sizes of the dispersed phases.With the increase of CB content,the tensile and bending strength of the composites increase significantly,while the impact strength decrease.The SAN/PCL/CB composites showed obvious gelation phenomenon,and its physical gel point is 6.5 wt%.The composites exhibits obvious conductive percolation behavior,the conductive percolation value is 4.9 wt%,the gel point obtained by the rheological method is located in the conductive percolation area,and is close to the conductive percolation value.(3)The addition of MWCNTs and MWCNTs-OH can reduce phase separation temperatures of the composites.The physical gel points of SAN/MWCNTs,SAN/PCL/MWCNTs,SAN/MWCNTs-OH,and SAN/PCL/MWCNTs-OH composites were 2.6 wt%,0.7 wt%,4.5 wt%,and 1.6 wt%,respectively.The composites with phase separation structure and MWCNTs with relative length to diameter ratios are easy to form gel network structure.The addition of MWCNTs and MWCNTs-OH can effectively improve the mechanical properties of these ternary composites.MWCNTsOH have strong interaction with SAN and exhibit high tougheness.SAN/MWCNTs,SAN/PCL/MWCNTs,SAN/MWCNTs-OH,and SAN/PCL/ MWCNTs-OH composites present obvious conductive percolation behaviors.The ternary composites have lower conductive percolation values,indicating that phase separation is in favour of the formation of conductive network.